Patients with central or branch retinal artery thrombosis of 6 hours or less who fail to respond to usual emergency measures to improve vision will be treated with streptokinase. In patients with retinal venous thrombosis of one week or less, effectiveness of thrombolytic therapy will be compared with that of heparin. History, fundoscopic examination and photography will be used in diagnosis and follow up. In addition, standard fluorescent angiography as well as dynamic analysis of flow rate by use of television monitoring will be performed before this start of treatment, during the treatment and subsequently to evaluate objectively the effect of thrombolytic therapy in the patient.